Merge #16521: rpc: Use the default maxfeerate value as BTC/kB

2dfd6834ef8737e16e4b96df0c459f30a0721d6c test: Add test for default maxfeerate in sendrawtransaction (Joonmo Yang)
261843e4bef96ab296a9775819a99bfa60cad743 wallet/rpc: Use the default maxfeerate value as BTC/kB (Joonmo Yang)

Pull request description:

  Fixes https://github.com/bitcoin/bitcoin/issues/16382

  This patch tries to treat `maxfeerate` in sendrawtransaction/testmempoolaccept RPC as a rate(BTC/kB) instead of an absolute value(BTC).
  The included test case checks if the new behavior works correctly, by using the transaction with an absolute fee of ~0.02BTC, where the fee rate is ~0.2BTC/kB.
  This test should be failing if the default `maxfeerate` is 0.1BTC, but pass if the default value is 0.1BTC/kB

ACKs for top commit:
  laanwj:
    ACK 2dfd6834ef8737e16e4b96df0c459f30a0721d6c (ACKs by Sjors and MarcoFalke above for trivially different code)

Tree-SHA512: a1795bffe8a182acef8844797955db1f60bb0c0ded97148f3572dc265234d5219271a3a7aa0b6418a43f73b2b2720ef7412ba169c99bb1cdcac52051f537d6af

5 files changed, 48 insertions, 26 deletions

diff --git a/src/rpc/rawtransaction.cpp b/src/rpc/rawtransaction.cpp
index 4003299662..461e8025da 100644
--- a/src/rpc/rawtransaction.cpp
+++ b/src/rpc/rawtransaction.cpp
@@ -14,6 +14,7 @@
 #include <node/coin.h>
 #include <node/psbt.h>
 #include <node/transaction.h>
+#include <policy/policy.h>
 #include <policy/rbf.h>
 #include <primitives/transaction.h>
 #include <psbt.h>
@@ -38,11 +39,11 @@
 
 #include <univalue.h>
 
-/** High fee for sendrawtransaction and testmempoolaccept.
- * By default, transaction with a fee higher than this will be rejected by the
- * RPCs. This can be overridden with the maxfeerate argument.
+/** High fee rate for sendrawtransaction and testmempoolaccept.
+ * By default, transaction with a fee rate higher than this will be rejected by
+ * the RPCs. This can be overridden with the maxfeerate argument.
  */
-constexpr static CAmount DEFAULT_MAX_RAW_TX_FEE{COIN / 10};
+static const CFeeRate DEFAULT_MAX_RAW_TX_FEE_RATE{COIN / 10};
 
 static void TxToJSON(const CTransaction& tx, const uint256 hashBlock, UniValue& entry)
 {
@@ -775,7 +776,7 @@ static UniValue sendrawtransaction(const JSONRPCRequest& request)
                 "\nAlso see createrawtransaction and signrawtransactionwithkey calls.\n",
                 {
                     {"hexstring", RPCArg::Type::STR_HEX, RPCArg::Optional::NO, "The hex string of the raw transaction"},
-                    {"maxfeerate", RPCArg::Type::AMOUNT, /* default */ FormatMoney(DEFAULT_MAX_RAW_TX_FEE),
+                    {"maxfeerate", RPCArg::Type::AMOUNT, /* default */ FormatMoney(DEFAULT_MAX_RAW_TX_FEE_RATE.GetFeePerK()),
                         "Reject transactions whose fee rate is higher than the specified value, expressed in " + CURRENCY_UNIT +
                             "/kB.\nSet to 0 to accept any fee rate.\n"},
                 },
@@ -805,19 +806,17 @@ static UniValue sendrawtransaction(const JSONRPCRequest& request)
         throw JSONRPCError(RPC_DESERIALIZATION_ERROR, "TX decode failed");
     CTransactionRef tx(MakeTransactionRef(std::move(mtx)));
 
-    CAmount max_raw_tx_fee = DEFAULT_MAX_RAW_TX_FEE;
+    CFeeRate max_raw_tx_fee_rate = DEFAULT_MAX_RAW_TX_FEE_RATE;
     // TODO: temporary migration code for old clients. Remove in v0.20
     if (request.params[1].isBool()) {
         throw JSONRPCError(RPC_INVALID_PARAMETER, "Second argument must be numeric (maxfeerate) and no longer supports a boolean. To allow a transaction with high fees, set maxfeerate to 0.");
     } else if (!request.params[1].isNull()) {
-        size_t weight = GetTransactionWeight(*tx);
-        CFeeRate fr(AmountFromValue(request.params[1]));
-        // the +3/4 part rounds the value up, and is the same formula used when
-        // calculating the fee for a transaction
-        // (see GetVirtualTransactionSize)
-        max_raw_tx_fee = fr.GetFee((weight+3)/4);
+        max_raw_tx_fee_rate = CFeeRate(AmountFromValue(request.params[1]));
     }
 
+    int64_t virtual_size = GetVirtualTransactionSize(*tx);
+    CAmount max_raw_tx_fee = max_raw_tx_fee_rate.GetFee(virtual_size);
+
     std::string err_string;
     AssertLockNotHeld(cs_main);
     const TransactionError err = BroadcastTransaction(tx, err_string, max_raw_tx_fee, /*relay*/ true, /*wait_callback*/ true);
@@ -841,7 +840,7 @@ static UniValue testmempoolaccept(const JSONRPCRequest& request)
                             {"rawtx", RPCArg::Type::STR_HEX, RPCArg::Optional::OMITTED, ""},
                         },
                         },
-                    {"maxfeerate", RPCArg::Type::AMOUNT, /* default */ FormatMoney(DEFAULT_MAX_RAW_TX_FEE), "Reject transactions whose fee rate is higher than the specified value, expressed in " + CURRENCY_UNIT + "/kB\n"},
+                    {"maxfeerate", RPCArg::Type::AMOUNT, /* default */ FormatMoney(DEFAULT_MAX_RAW_TX_FEE_RATE.GetFeePerK()), "Reject transactions whose fee rate is higher than the specified value, expressed in " + CURRENCY_UNIT + "/kB\n"},
                 },
                 RPCResult{
             "[                   (array) The result of the mempool acceptance test for each raw transaction in the input array.\n"
@@ -881,19 +880,17 @@ static UniValue testmempoolaccept(const JSONRPCRequest& request)
     CTransactionRef tx(MakeTransactionRef(std::move(mtx)));
     const uint256& tx_hash = tx->GetHash();
 
-    CAmount max_raw_tx_fee = DEFAULT_MAX_RAW_TX_FEE;
+    CFeeRate max_raw_tx_fee_rate = DEFAULT_MAX_RAW_TX_FEE_RATE;
     // TODO: temporary migration code for old clients. Remove in v0.20
     if (request.params[1].isBool()) {
         throw JSONRPCError(RPC_INVALID_PARAMETER, "Second argument must be numeric (maxfeerate) and no longer supports a boolean. To allow a transaction with high fees, set maxfeerate to 0.");
     } else if (!request.params[1].isNull()) {
-        size_t weight = GetTransactionWeight(*tx);
-        CFeeRate fr(AmountFromValue(request.params[1]));
-        // the +3/4 part rounds the value up, and is the same formula used when
-        // calculating the fee for a transaction
-        // (see GetVirtualTransactionSize)
-        max_raw_tx_fee = fr.GetFee((weight+3)/4);
+        max_raw_tx_fee_rate = CFeeRate(AmountFromValue(request.params[1]));
     }
 
+    int64_t virtual_size = GetVirtualTransactionSize(*tx);
+    CAmount max_raw_tx_fee = max_raw_tx_fee_rate.GetFee(virtual_size);
+
     UniValue result(UniValue::VARR);
     UniValue result_0(UniValue::VOBJ);
     result_0.pushKV("txid", tx_hash.GetHex());
diff --git a/test/functional/feature_segwit.py b/test/functional/feature_segwit.py
index b9db618575..d2826dd1b7 100755
--- a/test/functional/feature_segwit.py
+++ b/test/functional/feature_segwit.py
@@ -257,7 +257,7 @@ class SegWitTest(BitcoinTestFramework):
         tx.vin.append(CTxIn(COutPoint(int(txid2, 16), 0), b""))
         tx.vout.append(CTxOut(int(49.95 * COIN), CScript([OP_TRUE, OP_DROP] * 15 + [OP_TRUE])))  # Huge fee
         tx.calc_sha256()
-        txid3 = self.nodes[0].sendrawtransaction(ToHex(tx))
+        txid3 = self.nodes[0].sendrawtransaction(ToHex(tx), 0)
         assert tx.wit.is_null()
         assert txid3 in self.nodes[0].getrawmempool()
 
diff --git a/test/functional/mempool_accept.py b/test/functional/mempool_accept.py
index e19e249f21..dee7a04516 100755
--- a/test/functional/mempool_accept.py
+++ b/test/functional/mempool_accept.py
@@ -183,6 +183,7 @@ class MempoolAcceptanceTest(BitcoinTestFramework):
         self.check_mempool_result(
             result_expected=[{'txid': tx.rehash(), 'allowed': True}],
             rawtxs=[tx.serialize().hex()],
+            maxfeerate=0,
         )
 
         self.log.info('A transaction with no outputs')
diff --git a/test/functional/rpc_rawtransaction.py b/test/functional/rpc_rawtransaction.py
index 4338675270..d1ce97efff 100755
--- a/test/functional/rpc_rawtransaction.py
+++ b/test/functional/rpc_rawtransaction.py
@@ -432,17 +432,18 @@ class RawTransactionsTest(BitcoinTestFramework):
 
         self.log.info('sendrawtransaction/testmempoolaccept with maxfeerate')
 
+        # Test a transaction with small fee
         txId = self.nodes[0].sendtoaddress(self.nodes[2].getnewaddress(), 1.0)
         rawTx = self.nodes[0].getrawtransaction(txId, True)
         vout = next(o for o in rawTx['vout'] if o['value'] == Decimal('1.00000000'))
 
         self.sync_all()
         inputs = [{ "txid" : txId, "vout" : vout['n'] }]
-        outputs = { self.nodes[0].getnewaddress() : Decimal("0.99999000") } # 1000 sat fee
+        outputs = { self.nodes[0].getnewaddress() : Decimal("0.999990000") } # 10000 sat fee
         rawTx = self.nodes[2].createrawtransaction(inputs, outputs)
         rawTxSigned = self.nodes[2].signrawtransactionwithwallet(rawTx)
         assert_equal(rawTxSigned['complete'], True)
-        # 1000 sat fee, ~100 b transaction, fee rate should land around 10 sat/b = 0.00010000 BTC/kB
+        # 10000 sat fee, ~100 b transaction, fee rate should land around 100 sat/b = 0.00100000 BTC/kB
         # Thus, testmempoolaccept should reject
         testres = self.nodes[2].testmempoolaccept([rawTxSigned['hex']], 0.00001000)[0]
         assert_equal(testres['allowed'], False)
@@ -450,9 +451,32 @@ class RawTransactionsTest(BitcoinTestFramework):
         # and sendrawtransaction should throw
         assert_raises_rpc_error(-26, "absurdly-high-fee", self.nodes[2].sendrawtransaction, rawTxSigned['hex'], 0.00001000)
         # And below calls should both succeed
-        testres = self.nodes[2].testmempoolaccept(rawtxs=[rawTxSigned['hex']], maxfeerate='0.00070000')[0]
+        testres = self.nodes[2].testmempoolaccept(rawtxs=[rawTxSigned['hex']])[0]
         assert_equal(testres['allowed'], True)
-        self.nodes[2].sendrawtransaction(hexstring=rawTxSigned['hex'], maxfeerate='0.00070000')
+        self.nodes[2].sendrawtransaction(hexstring=rawTxSigned['hex'])
+
+        # Test a transaction with large fee
+        txId = self.nodes[0].sendtoaddress(self.nodes[2].getnewaddress(), 1.0)
+        rawTx = self.nodes[0].getrawtransaction(txId, True)
+        vout = next(o for o in rawTx['vout'] if o['value'] == Decimal('1.00000000'))
+
+        self.sync_all()
+        inputs = [{ "txid" : txId, "vout" : vout['n'] }]
+        outputs = { self.nodes[0].getnewaddress() : Decimal("0.98000000") } # 2000000 sat fee
+        rawTx = self.nodes[2].createrawtransaction(inputs, outputs)
+        rawTxSigned = self.nodes[2].signrawtransactionwithwallet(rawTx)
+        assert_equal(rawTxSigned['complete'], True)
+        # 2000000 sat fee, ~100 b transaction, fee rate should land around 20000 sat/b = 0.20000000 BTC/kB
+        # Thus, testmempoolaccept should reject
+        testres = self.nodes[2].testmempoolaccept([rawTxSigned['hex']])[0]
+        assert_equal(testres['allowed'], False)
+        assert_equal(testres['reject-reason'], '256: absurdly-high-fee')
+        # and sendrawtransaction should throw
+        assert_raises_rpc_error(-26, "absurdly-high-fee", self.nodes[2].sendrawtransaction, rawTxSigned['hex'])
+        # And below calls should both succeed
+        testres = self.nodes[2].testmempoolaccept(rawtxs=[rawTxSigned['hex']], maxfeerate='0.20000000')[0]
+        assert_equal(testres['allowed'], True)
+        self.nodes[2].sendrawtransaction(hexstring=rawTxSigned['hex'], maxfeerate='0.20000000')
 
 
 if __name__ == '__main__':
diff --git a/test/functional/wallet_basic.py b/test/functional/wallet_basic.py
index ce04110240..2283bff2e6 100755
--- a/test/functional/wallet_basic.py
+++ b/test/functional/wallet_basic.py
@@ -433,7 +433,7 @@ class WalletTest(BitcoinTestFramework):
         # Split into two chains
         rawtx = self.nodes[0].createrawtransaction([{"txid": singletxid, "vout": 0}], {chain_addrs[0]: node0_balance / 2 - Decimal('0.01'), chain_addrs[1]: node0_balance / 2 - Decimal('0.01')})
         signedtx = self.nodes[0].signrawtransactionwithwallet(rawtx)
-        singletxid = self.nodes[0].sendrawtransaction(signedtx["hex"])
+        singletxid = self.nodes[0].sendrawtransaction(signedtx["hex"], 0)
         self.nodes[0].generate(1)
 
         # Make a long chain of unconfirmed payments without hitting mempool limit